Morphological and anatomical observations on some precambrian plants from the Witwatersrand, South Africa

Precambrian uranium-bearing quartz-pebble conglomerates: exploration model and United States resource potential

“…In Canada, heavy minerals are concentrated in conglomerates which were deposited in topographic depressions that developed on the Archean erosion surface 4. Recent detailed studies of the organic material thucholite (Hallbauer, 1974(Hallbauer, , 1975 show that this material is some form of primitive plant, perhaps a primitive conidia producing fungus or some form of blue-green algae.…”

“…Its principal mode of occurrence is in mats that range in thickness from one to twelve millimeters, but it is also common as granules in conglomerate layers (Hallbauer, 1975). Placerists interpret this carbonaceous material to represent algal colonies which flourished near the mouths of the rivers and which collected gold and uranium by physically filtering the river water and, possibly, by chemically precipitating gold and uranium from solution.…”

“…In the Witwatersrand, the association of gold and uranium with carbonaceous seams suggests biochemical precipitation of mineralized waters (Pretorius, 1976b;Hallbauer, 1975) and textural studies of ore minerals suggest that some of the gold, uranium minerals, and pyrite are not of detrital origin (Saager, 1970;Feather and Koen, 1975;Simpson and Bowles, 1977). Similarly, in Canada, mineralogical and textural studies of the primary uranium mineral--brannerite--suggest that it may have formed by alteration of titanium phases in the presence of dissolved uranium (Ramdohr, 1957;Ferris and Rudd, 1971).…”

“…This type of gold was transported as detrital particles in sands and was incorporated in the matrix of gravels either by incorporation of underlying sands during deposition of gravels or by downward filtration of sands into previously deposited open-framework gravels (Pretorius, 1976b). The second type of gold occurs as veinlets and patches in the pores of carbonaceous material and as a replacement of the algal filaments in the columnar variety of carbonaceous material (Hallbauer, 1972(Hallbauer, , 1975. …”

Lichen preservation in amber: morphology, ultrastructure, chemofossils, and taphonomic alteration

“…Many reported finds have therefore been challenged for being notional and not proving evidence of a physiological interaction (see, for example, Waggoner, 1995;Taylor et al, 2009, for review). The oldest putative lichen fossil is 2.5 billion years old (Neoarchean) and consists of agglutinated hyphae around a central cord (Hallbauer et al, 1977); however, no photobionts were observed to conclusively prove a lichen nature (Matsunaga et al, 2013). The oldest generally accepted records of lichens derive from Early Devonian rocks.…”